Generally, a combustion apparatus including a boiler and a water heater having an internal circulation apparatus may be solely used, or compact combustion apparatuses may be connected in parallel with each other to configure a cascade system capable of having a capacity comparable with that of a large combustion apparatus.
Such a cascade system including a plurality of combustion apparatuses has advantages in which an installing at a limited space may be possible in comparison with a large combustion apparatus, a maintenance and a management may be easy, the cost of fuel may be reduced by operating some of the combustion apparatuses when a load is small and by additionally operating the rest of the combustion apparatuses as much as a required quantity of heat when the load is increased to require an increase of quantity of heat.
The cascade system using the plurality of combustion apparatuses may have a simplified exhaust pipe configuration using a common exhaust pipe. In other words, an exhaust flue connecting exhaust ports of the plurality of combustion apparatuses in parallel is used.
When such a common exhaust flue is used, gas discharged through the common exhaust flue may be flow reversely inside the combustion apparatus which has been stopped, and also a problem in which condensate water resulting from a condensation of vapor contained in the exhaust gas flows reversely may occur. The exhaust gas flowing inside the combustion apparatus flows into an indoor space. The reason is that the combustion apparatus has a configuration using a ventilator and the ventilator ventilates air inside the indoor space such that an inside of the combustion apparatus and the indoor space are actually in communication with each other.
With reference to the accompanying drawings, a configuration example of a typical combustion apparatus using a common exhaust flue will be described below.
FIG. 1 is a block diagram of a cascade system using a typical common exhaust flue.
With reference to FIG. 1, a typical cascade system is configured to include a plurality of combustion apparatuses 1, a reverse flow prevention portion 2 connected to an exhaust connection port 4 of each of the plurality of combustion apparatuses 1, and a common exhaust portion 3 discharging exhaust gas selectively discharged from each combustion apparatus 1 to an outside.
One side of the reverse flow prevention portion 2 is connected to the common exhaust portion 3, and the other side thereof is connected to the exhaust connection port 4 of the combustion apparatus 1.
As described above, the cascade system using the typical common exhaust flue includes the common exhaust portion 3 coupled to a plurality of reverse flow prevention portions 2 separated from the combustion apparatus 1, and has a configuration in which the exhaust connection port 4 of the combustion apparatus 1 is coupled to each of the reverse flow prevention portions 2.
A case of the reverse flow prevention portion 2 and the common exhaust portion 3 are generally formed with a polypropylene material having a relatively high hardness through a mold, and the reverse flow prevention portion 2 and the common exhaust portion 3 are manufactured by the same manufacturer to be supplied by being integrally coupled to each other.
Meanwhile, the common exhaust portion 3 may be certified in terms of a material, thermal resistance, durability, and the like. As described above, since the reverse flow prevention portion 2 is manufactured by a manufacturer the same as that of the common exhaust portion 3 and is supplied by being integrally coupled thereto, the reverse flow prevention portion 2 should be certified together with the common exhaust portion 3 so that a certification procedure may cause an inconvenience and a problem in an increase of time and costs may occur.
Also, in North America, it is permitted that a user purchases a relatively inexpensive polyvinyl chloride (PVC) pipe to use the PVC pipe as the common exhaust portion 3. As described above, however, since the reverse flow prevention portion 2 and the common exhaust portion 3 are manufactured by the same manufacturer to be supplied by being integrally coupled to each other, there is a problem in which a user residing in North America cannot afford to purchase a PVC pipe to use it as the common exhaust portion 3 of a cascade system excepting that a single combustion apparatus 1 is provided and thus the reverse flow prevention portion 2 is not required to allow the user to purchase the PCV pipe to use it as an exhaust flue.
FIGS. 2 and 3 are cross-sectional views illustrating a closing state and an opening state of the reverse flow prevention portion 2, respectively.
With reference to FIGS. 2 and 3 respectively, the typical reverse flow prevention portion 2 may be configured to include a first pipe 11 coupled to the exhaust connection port 4 of the combustion apparatus 1; a fixing member 12 provided at an inward center portion of the first pipe 1; a movable shaft 13 inserted into the fixing member 12 to be movable vertically; an opening and closing member 14 having a predetermined area, provided at an upper part of the movable shaft 13, and vertically moved according to a pressure difference between an upper part of the first pipe 11 and a lower part thereof to close the upper part thereof when having been moved in a downward direction; an escape prevention portion 15 provided at a lower end of the movable shaft 13 to prevent the movable shaft 13 from being escaped from the fixing member 12 in an upward direction; a second pipe 16 having a diameter greater than that of the first pipe 11 and provided at an upper side of the first pipe 11 to provide a space through which exhaust gas is discharged against the opening and closing member 14 when the opening and closing member 14 is moved in the upward direction; and a third pipe 17 extending from the second pipe 16 in the upward direction to be coupled to the common exhaust portion 3.
A protrusion sealing portion 18 protruding from the upper part of the first pipe 11 to come in contact with a lower edge of the opening and closing member 14 while the opening and closing member 14 has been closed is included.
In such a configuration, when the combustion apparatus 1 connected to a lower side of the first pipe 11 does not operate, a pressure of the common exhaust portion 3 through which exhaust gas is discharged is high due to an operation of other combustion apparatus 1, such that an internal pressure of the third pipe 17 becomes higher than that of the first pipe 11.
Consequently, as shown in FIG. 2, the opening and closing member 14 is moved in the downward direction and the lower edge thereof comes in contact with an upper part of the protrusion sealing portion 18 to close the upper part of the first pipe 11, thereby preventing a reverse flow of the exhaust gas flowing through the first pipe 11 into the combustion apparatus 1 located at the lower side of the first pipe 11.
Also, when the combustion apparatus 1 connected to the first pipe 11 operates, exhaust gas is discharged from the combustion apparatus 1 and thus the internal pressure of the first pipe 11 becomes higher than that of the third pipe 17 to push up the opening and closing member 14 in the upward direction.
When the opening and closing member 14 is upwardly moved inside the second pipe 16, the exhaust gas discharged through the first pipe 11 is discharged to the outside through a space between the opening and closing member 14 and the second pipe 16 along the third pipe 17 and the common exhaust portion 3.
As described above, the reverse flow prevention portion 2 applied to the cascade system using the typical common exhaust flue may perform an exhaust and a reverse flow prevention of the exhaust gas using a simplified configuration, but there is a problem in increasing a volume of the reverse flow prevention portion 2 because the second pipe 16 having a diameter greater than that of the first pipe 11 should be employed.
Also, since the opening and closing member 14 is vertically moved, a total area of the opening and closing member 14 nearly occludes the second pipe 16 so that it may cause a problem in which a discharge space defined by ‘d’ in FIG. 3 may be narrow to interrupt a smooth exhaust.
In addition, the opening and closing member 14 and the protrusion sealing portion 18, which are made of a plastic material, come in contact with each other to serve as a preventer of a reverse flow of the exhaust gas, so that there is a problem in which a complete occlusion of the reverse flow of the exhaust gas is difficult due to an insufficient sealing ability between plastics.
Moreover, upon an exhaust operation, condensate water resulting from a condensation of vapor contained in the exhaust gas may flow into the combustion apparatus 1 through the third pipe 17, the second pipe 16, and the first pipe 11, so that there is a problem in which a condensate water discharge apparatus including a siphon for discharging such condensate water should be separately provided.